The human eye functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea, and further focusing the image by way of a lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape and length of the eye, and the shape and transparency of the cornea and lens.
When trauma, age, disease or otherwise cause an individual's natural crystalline lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is often referred to as a cataract. The treatment for this condition is surgical removal of the natural crystalline lens and implantation of an intraocular lens (IOL).
While early IOLs were made from hard plastic, such as polymethylmethacrylate (PMMA), soft, foldable IOLs made from silicone, soft acrylics and hydrogels have become increasingly popular because of the ability to fold or roll these soft lenses and insert them through a smaller incision. Several methods of rolling or folding the lenses are used. One popular method is an injector cartridge that folds the lenses and provides a relatively small diameter lumen through which the lens may be pushed into the eye, usually by a soft tip plunger. One commonly used injector cartridge design is illustrated in U.S. Pat. No. 4,681,102 (Bartell), and includes a split, longitudinally hinged cartridge. Similar designs are illustrated in U.S. Pat. Nos. 5,494,484 and 5,499,987 (Feingold) and U.S. Pat. Nos. 5,616,148 and 5,620,450 (Eagles, et al.), the entire contents of which are incorporated herein by reference. Still other cartridges are described in U.S. Pat. No. 5,275,604 (Rheinish, et al.), U.S. Pat. No. 5,653,715 (Reich, et al.) and U.S. Pat. No. 5,947,876 (Van Noy, et al.), the entire contents of which are incorporated herein by reference.
As an IOL is pushed by a plunger through a small diameter lumen of the cartridge, relatively large amounts of force can be placed upon the plunger, the cartridge and/or the IOL. Generally, it is desirable to have the cartridge manage these forces to promote effective delivery of an IOL. These forces have recently become an increasing concern. In particular, the medical community has expressed a desire for IOL cartridges to have smaller nozzles, which in turn allows a surgeon to use a smaller incision for delivery of an IOL to an individual's eye. These smaller nozzles result in smaller lumens through which the IOL must be pushed during IOL delivery. Therefore, the forces placed on the IOL, the cartridge nozzle and the plunger during delivery of the IOL can be significantly increased and management of these forces can be challenging.
To alleviate forces that occur during IOL delivery, low friction coatings are often applied to the internal surface of the cartridges to allow the IOL to more easily pass through the lumen defined by that internal surface. However, conventional coatings for IOL cartridges can be complex to apply and can involve multiple layers and multiple different materials. In turn, such coatings can be difficult to apply in a consistent manner and can take up space of the lumen through which the IOL would normally pass.
In addition to coatings, management of IOL delivery forces can also be accomplished through the use of materials that are capable of handling those forces, particularly materials for the delivery cartridge. However, it is extremely challenging to find a material that is suitable for insertion into any eye and exhibits the desired physical properties for handling IOL delivery forces while, at the same time, is compatible with a coating that is to be applied to an internal surface of the IOL delivery cartridge.
In view of the above, it would be desirable to provide an IOL cartridge and coating combination where the coating is improved relative to conventional coatings and the material that forms the cartridge is compatible with the improved coating while still exhibiting desirable physical properties.